228 Harland G. Wood 



In animals it is now well established that a labelled sub- 

 strate which gives rise to carboxyl-labelled "acetate"* or 

 pyruvate gives rise in turn to a 3, 4-labelled glucose, and a 

 substrate that yields methyl-labelled "acetate" leads to the 

 formation of a sugar labelled equally in the 1, 2, 5 and 6 

 positions. If pyruvate or lactate with the highest labelling 

 in the beta position is fed or formed, the glucose is labelled 

 highest in the 1, 6 positions; on the other hand if the labelling 

 is highest in the alpha position the 2, 5 positions of the sugar 

 contain the most tracer. Thus far the distributions found in 

 animals have been uniformly in accord with present concepts 

 of glycolysis and oxidation by the tricarboxylic acid cycle. f 



♦"Acetate," "formate" and "pyruvate" denote the compound itself or a 

 metabolite thereof which is the active form of the compound. 



fThere most likely are other mechanisms of breakdown but apparently they 

 either are not of major quantitative significance or the present method with 

 glycogen is not suitable to detect them. For example, there is considerable 

 evidence of a terminal oxidation of glucose to phosphogluconic acid and its 

 breakdown by subsequent decarboxylation (Dickens, 1938; Scott and Cohen, 

 1951; Horecker and Smyrniotis, 1950). Of interest in this respect are the 

 observations of Gibbs and Gunsalus (private communication) with Leiiconostoc 

 mesenteroides. They have shown that these bacteria ferment [l-^^C]-glucose 

 to the folloAving products: — 



i4C-C-C-C-C-C->i4C02 + CHg CH2OH + COOH CHOH CHj 

 12 3 4 5 6 



Contrary to the usual alcoholic type of fermentation the CO2 in this case 

 arises from the 1 position. AVith [3,4-^^C]-glucose the labelling was: — 



C-C-i*C-"C-C-C^C02 + CH3 i^CHoOH + i^COOH CHOH CH3 

 12 3 4 5 6 



If the above conversions were reversible it would be expected that CO, would 

 enter position 1 of the glucose. Apparently such a reversible conversion does 

 not occur in rats, or if it does so it must be slow in the liver. Shreeve, Feil, 

 Lorber and Wood (1949) considered that there was some activity in the 

 1, 2, 5, 6 positions of liver glycogen but Gibbs, Dumrose, Bennet and Bubeck 

 (1950) have shown that the bacterial degradation to lactate is not completely 

 specific and this non-specificity may account for the findings of Shreeve et al. 

 (1949). Gibbs et al. found about 3 per cent of the 3, 4 position of glucose to 

 be converted to the methyl group of lactate during the fermentation. It is 

 not yet clear how the small amount of tracer gets into the 2, 5 position of the 

 glucose or the a-carbon of lactate. This in itself is an interesting problem. 

 In support of the view that COg is only fixed in the 3, 4 position. Topper and 

 Hastings (1949) have found, using liver slices, that there is no detectable 

 fixation of COj in the 1 and 2 positions of the glucose of glycogen. A chemical 

 degradation was employed in this case and the activity in the sugar was high 



